This invention relates to coatings for molds used in casting metal parts and, more particularly, to a refractory mold coating for metal molds used in casting iron, steel and other alloys.
Refractory mold coatings have been used for various types of metal casting molds to enhance the smoothness and uniformity of the casting surface. The refractory coating typically is applied to the molding surfaces as a slurry, such as by spraying, dipping and drying, and allowed to dry to a hardened state prior to pouring molten metal into the mold.
Examples of prior refractory mold coatings are disclosed in U.S. Pat. Nos. 1,886,249 (Bensing), 2,544,598 (Kalina), 3,243,397 (Herkimer et al), 3,436,235 (Baer et al), and 3,447,936 (Ornitz). While generally satisfactory, these coatings tend to have one or more of the following shortcomings: do not adhere sufficiently to the mold surfaces to withstand the washing away action as the molten metal is being poured into the mold, adhere strongly to the casting and makes stripping difficult, poor resistance to burn through with a resulting erosion of the mold, require multiple applications, excessively long drying time, and solids in coating tend to settle within relatively short time periods during storage. Other refractory compositions for different mold applications are disclosed in U.S. Pat. Nos. 3,059,296 (North) and 3,859,153 (Beyer et al).